Windows XP Service Pack 3

Hello, I'm having issues with my service pack. I removed it and am now running SP2. I thought that would fix my issues but it didn't. So now I want to put SP3 back in and now I can't. I'm getting this error message.

Service pack 3 Setup Error
The file c:\windows\system32\drivers\usbcamd\sys is open or in use by another application.
Close all other applications and then click retry

The issue is, nothing else is open. How can I reinstall SP3? I'd like to get this corrected today. I can't run IE8 (probably becuase I'm on SP2 now) and I'm having a few other issues.